WO2003012784A1 - Support d'enregistrement optique, procede de realisation, et resine protective filmogene - Google Patents

Support d'enregistrement optique, procede de realisation, et resine protective filmogene Download PDF

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Publication number
WO2003012784A1
WO2003012784A1 PCT/US2002/023070 US0223070W WO03012784A1 WO 2003012784 A1 WO2003012784 A1 WO 2003012784A1 US 0223070 W US0223070 W US 0223070W WO 03012784 A1 WO03012784 A1 WO 03012784A1
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WIPO (PCT)
Prior art keywords
protective film
resin
surface treatment
substrate
forming resin
Prior art date
Application number
PCT/US2002/023070
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English (en)
Inventor
Kazuta Saito
Katsuya Takamori
Original Assignee
3M Innovative Properties Company
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
Application filed by 3M Innovative Properties Company filed Critical 3M Innovative Properties Company
Priority to US10/484,281 priority Critical patent/US20040184397A1/en
Publication of WO2003012784A1 publication Critical patent/WO2003012784A1/fr

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Classifications

    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
    • G11B7/252—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers
    • G11B7/257—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of layers having properties involved in recording or reproduction, e.g. optical interference layers or sensitising layers or dielectric layers, which are protecting the recording layers
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
    • G11B7/252—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers
    • G11B7/254—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of protective topcoat layers
    • G11B7/2542—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of protective topcoat layers consisting essentially of organic resins
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
    • G11B7/242—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers
    • G11B7/243—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising inorganic materials only, e.g. ablative layers
    • G11B2007/24302—Metals or metalloids
    • G11B2007/2431—Metals or metalloids group 13 elements (B, Al, Ga, In)
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
    • G11B7/252—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers
    • G11B7/253—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of substrates
    • G11B7/2533—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of substrates comprising resins
    • G11B7/2534—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of substrates comprising resins polycarbonates [PC]

Definitions

  • the present invention relates to an optical recording medium and, more particularly, to an optical recording medium having a protective film provided on an information recording layer formed on a substrate.
  • the optical recording medium is typically an optical disk.
  • the present invention also relates to a method of producing an optical recording medium and a protective film-forming resin used in such a method.
  • Moving pictures and audio data generally contain a vast amount of information and therefore require a large capacity and high density medium to record them.
  • optical disks such as DVD (digital versatile disk) and CD (compact disk) are considered to be promising for their capability to meet the future requirements for further larger capacity and higher recording density.
  • An optical disk typically comprises a substrate and an information recording layer and protective layer which are formed in order on the substrate, as will be easily understood from the detailed description of an optical disk of the present invention which will be given below with reference to the accompanying drawings.
  • a read-only optical disk for example, comprises a disk-shaped substrate (made of polycarbonate resin, for instance) having pits which carry information on guide grooves formed on the surface thereof, deposited by an information recording layer made of aluminum or the like.
  • the surface of the information recording layer is coated with a protective film made of a light transmitting resin in order to protect the optical disk from atmospheric moisture and mechanical damage. Reproduction of information from such an optical disk can be carried out by continuously irradiating the information pits on the guide grooves of the substrate with laser beam focused thereon by means of an object lens used for reproduction pickup.
  • the protective film must have a high transparency to the reproducing light as the information is reproduced by means of irradiation with light.
  • the protective film is required to be as thin as possible and have substantially uniform thickness over the entire surface of the recording medium with the surface being smooth.
  • the conventional protective film does not fully satisfy these requirements.
  • the protective film of the optical disk is usually formed by, for example, applying an ultraviolet curing resin to the surface of the information recording layer to a predetermined thickness by the spin coating process, then curing the resin by irradiating with ultraviolet radiation.
  • the protective film 3 formed on the surface of the substrate 1 made of polycarbonate resin tends to be thinner near the center of the disk and thicker near the periphery, with a ridge being formed along the periphery because the substrate 1 is rotated during spin coating.
  • the ridge is typically 1 to 2 millimeter (mm) in width and 20 to 30 micrometer ( ⁇ m) in height.
  • Such a variation in the film thickness has an adverse effect on the reproduction characteristic and, in the case where a magnetic head is used as the reproducing means, may cause head crash or the like. Also a defect of radial configuration is likely to occur which is characteristic to the film forming technique by means of the spin coating process.
  • a protective sheet in which a disk-shaped sheet is punched out of a protective film sheet (made of polycarbonate, for instance) which is about 70 to 90 ⁇ m in thickness, and is laminated to the surface of the information recording layer of an optical disk via an adhesive agent or an adhesive sheet.
  • a protective film sheet made of polycarbonate, for instance
  • the adhesive agent used in this technique is typically an ultraviolet curing resin which has an intrinsic drawback of variation being caused in the thickness of the adhesive layer. In case an adhesive sheet is used, there arises a problem of disposing of a release liner, as well as the high cost of the sheet due to the special quality thereof.
  • An object of the present invention is to provide an optical recording medium having high quality which overcomes the problems of the prior art described above, has a protective film which is thin with no variation in the film thickness and has a smooth surface, thereby satisfies the requirements for larger capacity and higher density.
  • Another object of the present invention is to provide a method of producing the optical recording medium of high quality, which has a protective film which is thin with no variation in the film thickness and has a smooth surface, easily and at a low cost.
  • Still another object of the present invention is to provide a method of producing the optical recording medium which is free from such troubles as dust depositing on the protective film, scratches, bending, and defects in radial direction.
  • the present invention provides, in one aspect, an optical recording medium comprising a substrate, an information recording layer formed on the substrate, and a protective film made of a light transmitting resin provided on the surface of the information recording layer.
  • the protective film has a substantially uniform thickness in a range from 50 to 200 ⁇ m, and has a surface which reproduces the smoothness of the surface of a surface treatment medium which has been covering the surface of the protective film during the formation thereof.
  • the present invention provides, in another aspect, a method of producing an optical recording medium comprising a substrate, an information recording layer and a protective film which are formed in order on the substrate.
  • the method which comprises the steps of:
  • the present invention provides a protective film for an optical recording medium, comprising a protective film-forming photocurable resin.
  • the photocurable resin is cured by light which has transmitted through an adjacent medium thereby to form the protective film.
  • the optical recording medium of the present invention since the space between the substrate and the surface treatment medium which are disposed in parallel to each other is filled with the protective film-forming resin which is then cured, the production process can be simplified.
  • the thickness of the protective film can be easily decreased, while the thickness can be made substantially uniform.
  • the surface treatment medium which has excellent flatness and smoothness the flatness and smoothness of the surface treatment medium can be accurately transferred onto the surface of the protective film, and the radial defects encountered with the spin coating process of the prior art can be prevented from occurring.
  • the protective film- forming resin is inexpensive and readily available commercially, the production cost can be kept far lower than that of the prior art.
  • Fig. 1 is a cross sectional view showing problems during the formation of a protective film in a method of producing an optical disk of the prior art.
  • Fig. 2 is a cross sectional view showing schematically one embodiment of the optical disk of the present invention and use thereof.
  • Fig. 3 (A) to (D) are cross sectional views showing in sequence one preferred method of producing the optical disk according to the present invention.
  • Fig. 4 (A) to (D) are cross sectional views showing in sequence another preferred method of producing the optical disk according to the present invention.
  • optical recording medium of the present invention may have various constructions according to the method of recording and reproducing the information which is employed, it is basically constituted to include at least:
  • optical recording media is an optical disk such as CD and DVD.
  • the protective film of the optical recording medium according to the present invention may also be used in any fields other than the optical recording medium as required, by making use of the good quality thereof.
  • Fig. 2 is a perspective view showing an embodiment of read-only optical disk (DVD) according to the present invention.
  • the optical disk 10 comprises a substrate 1 made of a transparent resin (polycarbonate resin, for instance), with a pattern of pits (not shown) corresponding to given information being formed on the surface of the transparent substrate 1.
  • the optical disk 10 has a circular hole (aperture) made at the center thereof.
  • the aperture of the optical disk is fitted with a shaft of the apparatus.
  • an information recording layer 2 which is made of a metal such as aluminum and has reflectivity of around 90%.
  • Surface of the information recording layer 2 is coated with a protective film 3 made of a light transmitting resin in order to protect the information recording layer from the atmospheric moisture and mechanical damage.
  • Reproduction of information from the optical disk 10 can be carried out by irradiating the optical disk with a laser beam L from an optical head (not shown) and receiving the light reflected from the information pits of the information recording layer 2.
  • optical disk of the present invention is not limited to this embodiment.
  • the optical disk of the present invention may also be an optical disk which allows both recording and reproduction of information, or an optical disk having the information recording layer and the protective film provided thereon on both sides of the substrate.
  • the optical disk of the present invention may be an optical disk which utilizes magneto-optical phenomenon or phase change for recording and reading information.
  • the substrate which carries the information recording layer.
  • the substrate may be transparent, semi-transparent or opaque depending on the method of recording and reading information which is employed.
  • the substrate may be formed from a plastic material such as acrylic resin and polycarbonate resin by an ordinary molding method such as injection molding process, as is common in this technical field. Alternatively, a material other than the plastic material, i.e., glass and others, for example, may be used in some cases.
  • the substrate may be made in various sizes depending on the size of the optical recording medium required. For example, in the case of the commercially available optical recording medium such as DVD, the substrate is 12 centimeters (cm) in diameter and 0.6 mm in thickness.
  • the optical recording medium may also have a shape other than a disk shape, if necessary.
  • the surface whereon the information recording layer is formed has a pattern of grooves or pits, which correspond to the signals which represent the image or sound to be recorded on the optical recording medium, formed thereon.
  • the pattern of pits may be formed by master stamping or photolithogaphy.
  • the pattern of pits may not necessarily be formed on the substrate surface depending on the method of recording and reading information.
  • the information recording layer is usually formed in a thin film from a metallic or ceramic material suitable for forming a reflective or semi- transparent recording layer.
  • Materials suitable for forming the information recording layer of reflecting type include those having a reflectivity of around 90% after the film has been formed, for example, aluminum.
  • Materials suitable for forming the semi-transparent recording layer include those having a reflectivity of around 50% after the film has been formed, for example, gold, silicon-based dielectric material (including silicon nitrides generally represented by SiNx or SiC, etc.). These materials may be formed into the recording layer by the ordinary thin film forming techniques such as sputtering and vacuum vapor deposition processes. Thickness of the information recording layer may be selected from a wide range, but is typically in a range from about 10 to 500 nanometers (nm).
  • the protective film provided on the top of the optical recording medium is formed from a light-curable resin, i.e. the resinous material curable upon light irradiation.
  • a light-curable resin i.e. the resinous material curable upon light irradiation.
  • the term "light” used herein is intended to mean different types of light including radiations such as visible light and UV light, and electron beam and others.
  • the light-curable resin materials suited for forming the protective film include, for example, ultraviolet (UV)-curing resin and electron beam (EB)-curing resin.
  • Appropriate light- curable resins include, but not limited to, acrylic compounds such as isooctyl
  • (meth)acrylate 2-ethylhexylcarbitol (meth)acrylate, n-butyl (meth)acrylate, isostearyl (meth)acrylate and other (meth)acrylic esters, urethane acrylate, epoxy acrylate, polyester acrylate and others.
  • a light-curable resin is typically used in combination with a photopolymerization initiator.
  • Particularly preferred ultraviolet-curing resin comprises a mixture of urethane acrylate and dimethylol tricyclodecane diacrylate, or a mixture of urethane acrylate and 1 ,6-hexanediol diacrylate, with a photopolymerization initiator added thereto.
  • additives generally used in this technical field may be incorporated into the resins described above.
  • suitable additives include, for example, a thickening agent, a plasticizer, a dispersing agent, a polymerization inhibitor and the like.
  • the protective film-forming resins described above are generally coated and cured on a surface of the information recording layer formed over the substrate.
  • the protective film-forming resins may be coated and cured on a surface of the surface treatment medium, in addition to the surface of the information recording layer. If this double surface coating method is used in the production of the optical recording medium, for examples, it becomes possible to easily control a thickness of the resulting protective film.
  • the same resin may be coated on both of the surface of the information recording layer and the surface of the surface treatment medium, or the resins having different compositions, properties and others may be coated on the surface of the information recording layer and that of the surface treatment medium. For example, if the resins having different adhesion strengths to the adherent, an operation of separating the recording medium from the surface treatment medium can be improved.
  • the protective film-forming resin may be applied by other coating methods or film formation methods as required, it is advantageous to apply the resin onto the information recording layer and others by the spin coating process.
  • the spin coating process may be carried out by using a spin coater which is commercially available and under the conventional coating conditions.
  • the protective film-forming resin has viscosity typically 1 ,000 centipoises (cps) or higher, preferably in a range from 2,000 to 100,000 cps, more preferably in a range from 5,000 to 100,000 cps. These values of viscosity are preferred because the optical recording medium of the present invention is made by coating the substrate surface and, if necessary, a surface treatment medium with a selected resin to a uniform thickness by the spin coating process or the like, and then laminating the surface treatment medium therewith with care so as not to allow the thickness of the resin layer to change. For this reason, viscosity of the resin is desired to be high. However, viscosity of the resin must be kept within such a level which allows practical application operation.
  • cps centipoises
  • a resin having a viscosity which is too low may flow and drip from the periphery of the substrate before being cured after application.
  • the viscosity less than 1 ,000 cps causes a variation in the thickness of the resulting protective film, while the viscosity above 100,000 cps suffers from difficulty of coating.
  • the viscosity of the protective film-forming resin referred to in the specification, was determined at 25°C using a
  • Brookfield viscometer (BM#2 spindle, 12 revolutions per minute (rpm)) according to Japanese Industrial Standard JIS K 7117-1-1999.
  • the surface treatment medium After applying a predetermined amount of the protective film-forming resin onto the information recording layer, the surface treatment medium is laminated onto the substrate so as to sandwich the uncured resin layers at a desired and uniform thickness corresponding to that of the protective film, followed by curing of the resin.
  • the amount of the resin required for the formation of the protective film is a total of this additional resin and the resin applied to the information recording layer.
  • the resin is an ultraviolet- curing resin
  • a thin glass sheet (disk) having good transparency to ultraviolet rays and a smooth surface is used as the surface treatment medium.
  • the resin is cured by irradiating the resin with ultraviolet rays emitted by a high pressure mercury lamp through the glass sheet.
  • a plastic sheet or other materials may be used as the surface treatment medium.
  • the double surface coating method can be advantageously carried out with different embodiments.
  • the same or different resins may be used on the information recording layer and on the surface treatment medium.
  • curing of the coated resin may be carried out after lamination of the substrate and the surface treatment medium or, alternatively, either one of the resin on the information recording layer and the resin on the surface treatment medium may be first cured, and the remaining resin is then cured after lamination of the substrate and the surface treatment medium.
  • a diameter of the surface treatment medium may be controlled to have a larger size than the surface of the substrate for supporting the information recording medium.
  • the resin is coated on an overall surface of the surface treatment medium, the area, corresponding to the information recording layer, of the coated resin is selectively cured and the uncured resin is removed from the surface treating medium, followed by laminating the surface treatment medium to the substrate.
  • a thickness distribution of the protective film can be easily controlled, along with prevention of shifting in the laminated product and increase of working efficiency.
  • the protective film of the optical recording medium the protective film has a thickness typically in a range from about 50 to 200 ⁇ m, preferably from about 60 to 150 ⁇ m.
  • the protective film has thickness that is substantially uniform over the entire surface thereof. That is, when the protective film is 100 ⁇ m thick, tolerance of the thickness is typically in a range of 100 ⁇ 3 ⁇ m.
  • the protective layer also has preferably excellent surface flatness and smoothness.
  • the smooth surface of the surface treatment medium may display a wide range of surface energies such that, upon removal of the same, the highest surface energy of the surface treatment medium surface in contact with the cured protective film-forming resin does not disrupt the cured resin surface so as to disallow for the optical recording media's intended use. Similarly the lowest surface energy of the surface treatment medium surface in contact with the uncured resin does not disallow wetting out of the intended surfaces or impede resin flow on or between the same.
  • the optical recording medium of the present invention comprises the substrate, the information recording layer and the protective film. In addition, it may also have other additional layers such as a printed layer, a non-reflection coat layer, a hard coat layer, an antistatic layer and others.
  • the optical recording medium of the present invention can be produced advantageously by forming the protective film in the following procedure after conventionally forming the information recording layer on the substrate.
  • the protective film-forming resin having a light transmitting property is applied to the surface of the information recording layer formed on the substrate.
  • the selected resin is caused to drip through a nozzle while rotating the substrate using a spin coater or the like, thereby forming a thin film of the selected resin on the substrate.
  • the quantity of the resin to be applied is preferably such that is sufficient to form the protective film with a desired thickness of 50 to 200 ⁇ m.
  • the protective film-forming resin may be applied to a surface
  • The_protective film-forming resin applied to the surface of the surface treatment medium may be the same as or different from the resin applied to the surface of the information recording layer.
  • the sum of the amount of the resin applied onto the both surfaces is equal to the amount required to obtain the desired thickness in the protective film.
  • the surface treatment medium used herein has the function of transferring its surface smoothness and therefore may also be called a mold. While detailed characteristics of the surface treatment medium are not limited, the mold surface is required to have a level of smoothness which corresponds to the required smoothness of the protective film. In case a light-curing resin is used, the mold must transmit light, for example ultraviolet rays, to cure the resin.
  • a proper material for the surface treatment medium having light transmitting property includes a glass disk and a plastic sheet.
  • the surface of the surface treatment medium may be subjected to release treatment such as the application of a silicone resin in order to facilitate the release of a surface treatment medium from a substrate after curing the protective film.
  • the surface of the surface treatment medium may have a previously formed layer of the protective film-forming resin.
  • the protective film-forming resin is cured while being sandwiched between the substrate and the surface treatment medium.
  • the method and conditions of curing can be selected from wide ranges in accordance to the type of resin and other factors.
  • the resin can be cured by irradiating with ultraviolet rays via the surface treatment medium (glass disk) thereby to form the protective film.
  • the surface smoothness of the surface treatment medium is transferred onto the surface of the protective film.
  • either one of the two resin layers may be previously cured before the substrate and the surface treatment medium are stacked as described above.
  • another uncured resin layer is cured.
  • the curing methods and conditions may be optionally changed.
  • the surface treatment medium used to render smoothness is removed, leaving the protective film having a smooth surface being obtained.
  • the surface treatment medium which has been removed can be reused after being cleaned, thus allowing economical producing operation.
  • An optical disk substrate was produced by applying an information recording layer, in a thickness of 50 nm, by sputtering of aluminum onto a transparent circular substrate made of polycarbonate. Then, as shown in the step (A) of Fig. 3, a UV curing syrup 3 was dripped through a nozzle 13 on the nearly center portion of the surface of the disk substrate 1 (information recording layer is not shown) while rotating the disk substrate 1.
  • the syrup 3 used herein was prepared by mixing 30 parts of urethane acrylate (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.
  • UV6100B 70 parts of dimethylol tricyclodecane diacrylate and 5 parts of a photopolymerization initiator (manufactured by CIBA-GEIGY Ltd. under the trade name of Darocure 1173 1 M ).
  • a thin film of the UV curing syrup 3 was formed on the surface of the disk substrate 1.
  • a circular glass sheet 5 (1 mm in thickness) having the same shape and size as those of the disk substrate 1 was laminated on the surface at a side of the syrup 3 of the disk substrate 1.
  • the surface of the glass sheet 5 was previously subjected to a smoothing treatment to impart the same level of the smoothness as that of the required smoothness of the protective film.
  • the state where the disk substrate 1 and the glass sheet 5 are placed on upon another were retained until the UV curing syrup 3 naturally spreads over the entire disk substrate.
  • the UV curing syrup 3 was irradiated with ultraviolet rays (wavelength of 200 to 400 nm) via the glass sheet 5 for ten seconds, thereby to completely cure the syrup.
  • the glass sheet 5 was removed from the disk substrate 1 by the hand to obtain an optical disk having an about 100 ⁇ m-thick protective film on the surface.
  • the thickness of a protective film of the optical disk sample was measured based on the specified measuring conditions in a non-destructive and non-contact manner, using a thickness measuring device equipped with a multi-focal optical sensor manufactured by KEYENCE Corporation, Osaka, Japan. As a result, the measurement results as shown in
  • Table 1 were obtained.
  • average thickness ( ⁇ m) means an average thickness of thicknesses of protective films of two samples
  • variation in film thickness (difference between maximum value and minimum value, ⁇ m) means an average value with respect to the whole optical disk and a measured value with respect to each of six kinds of tracks (Tr. 1 to Tr. 6) having different circumferences and radiuses.
  • the surface smoothness of the protective film of the optical disk sample was measured with regard to the surface roughness.
  • the surface roughness of the protective film was measured using a laser confocal microscope, available from KEYENCE Corporation, Osaka, Japan, as Model Number VF-750.
  • the instrument incorporates software which calculated the average surface roughness as "Ra" of the surface according to JIS B 0601-1994.
  • the average surface roughness Ra recorded in micrometers ( ⁇ m) is defined as the surface smoothness of several individual measurement areas determined according to JIS B 0601-1994. The measurement results as shown in Table 1 were obtained.
  • An optical disk substrate was produced by applying an information recording layer in a thickness of 50 nm by sputtering aluminum onto a transparent circular substrate made of polycarbonate. Then, as shown in the step (A) of Fig. 4, a UV curing syrup 3 was dripped through a nozzle 13 on the nearly center portion of the surface of the disk substrate 1 (information recording layer is not shown) in the form of as a doughnut while rotating the disk substrate 1.
  • the syrup 3 used herein was prepared by mixing 60 parts of urethane acrylate (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.
  • UV6100B 40 parts of 1,6-hexanediol diacrylate and 5 parts of a photopolymerization initiator (manufactured by CIBA-GEIGY Ltd. under the trade name of Darocure 1173 ).
  • a doughnut-like thin film of the UV curing syrup 3 was formed on the surface of the disk substrate 1.
  • a circular glass sheet (1 mm in thickness) having the same shape and size as those of the disk substrate 1 was laminated on the surface of the syrup 3 of the disk substrate 1.
  • the surface of the glass sheet 5 was previously subjected to a smoothing treatment to impart the same level of the smoothness as that of the required smoothness of the protective film.
  • the disk substrate 1 and the glass sheet 5 were placed on upon another, and then excess UV curing syrup 3 was removed while rotating at high speed in the direction shown by the arrow. As a result, a thin film having a predetermined thickness made of the UV curing syrup 3 was formed.
  • the UV curing syrup 3 was irradiated with ultraviolet rays (wavelength of 200 to 400 nm) through the glass sheet 5 for ten seconds, to completely cure the syrup.
  • the glass sheet 5 was removed from the disk substrate 1 by hand to obtain an optical disk having an about 100 ⁇ m-thick protective film on its surface.
  • Example 2 In the same procedure as in Example 1 , a series of evaluation tests were carried out. As a result, the measurement results as described in Table 1 were obtained.
  • Example 2 The same procedure as in Example 1 was repeated, except that the surface of a disk substrate was spin-coated with a UV curing syrup in a thickness of 100 ⁇ m and the syrup was completely cured by irradiating with ultraviolet rays (wavelength of 200 to 400 nm) for ten seconds, for comparison.
  • a glass sheet was not used as a mold for transferring the smoothness.
  • Example 2 In the same procedure as in Example 1 , a series of evaluation tests were carried out. As a result, the measurement results as described in Table 1 were obtained.
  • Example 2 The same procedure as in Example 1 was repeated, except that a protective film was formed by bonding a polycarbonate sheet (thickness of about 70 ⁇ m) onto the surface of the disk substrate through by means of a pressure-sensitive adhesive layer (thickness of about 30 ⁇ m) in place of forming a protective film derived from the UV curing syrup on the disk substrate, for comparison.
  • a protective film was formed by bonding a polycarbonate sheet (thickness of about 70 ⁇ m) onto the surface of the disk substrate through by means of a pressure-sensitive adhesive layer (thickness of about 30 ⁇ m) in place of forming a protective film derived from the UV curing syrup on the disk substrate, for comparison.
  • Example 2 In the same procedure as in Example 1 , a series of evaluation tests were carried out. As a result, the measurement results as described in Table 1 were obtained.
  • an optical recording medium of a high quality which has a protective film that is thin with little variation in the film thickness and has a smooth surface, thereby to satisfy the requirements for larger capacity and higher density recording medium.
  • an optical recording medium of a high quality can be produced, easily and at a low cost.

Abstract

L'invention concerne un support d'enregistrement optique (10) qui comprend un substrat (1) et une couche d'enregistrement d'informations (2) sur ce substrat. La surface de ladite couche (2) comporte un film protecteur (3) en résine qui transmet la lumière. Le film (3) présente une épaisseur sensiblement uniforme, dans une gamme comprise entre 50 et 200 νm, et la surface du film reproduit le caractère lisse de la surface d'un moyen de traitement de surface utilisé pour recouvrir la surface de ladite couche (3) durant sa réalisation.
PCT/US2002/023070 2001-07-27 2002-07-22 Support d'enregistrement optique, procede de realisation, et resine protective filmogene WO2003012784A1 (fr)

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EP1542220A2 (fr) * 2003-12-09 2005-06-15 Fuji Photo Film Co., Ltd. Support d' enregistrement optique d' informations, méthode de fabrication de support d' enregistrement optique d' informations, et méthode d' enregistrement optique d' informations
US7799885B2 (en) 2005-11-30 2010-09-21 Corning Incorporated Photo or electron beam curable compositions
US8192821B2 (en) 2006-07-10 2012-06-05 Nippon Kayaku Kabushiki Kaisha Ultraviolet-curable resin composition and use thereof

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1542220A2 (fr) * 2003-12-09 2005-06-15 Fuji Photo Film Co., Ltd. Support d' enregistrement optique d' informations, méthode de fabrication de support d' enregistrement optique d' informations, et méthode d' enregistrement optique d' informations
EP1542220A3 (fr) * 2003-12-09 2006-03-01 Fuji Photo Film Co., Ltd. Support d' enregistrement optique d' informations, méthode de fabrication de support d' enregistrement optique d' informations, et méthode d' enregistrement optique d' informations
CN100405486C (zh) * 2003-12-09 2008-07-23 富士胶片株式会社 光信息记录介质及其制造方法、以及光信息记录方法
US7799885B2 (en) 2005-11-30 2010-09-21 Corning Incorporated Photo or electron beam curable compositions
US8088877B2 (en) 2005-11-30 2012-01-03 Corning Incorporated Photo or electron beam curable compositions
US8557941B2 (en) 2005-11-30 2013-10-15 Corning Incorporated Photo or electron beam curable compositions
US8192821B2 (en) 2006-07-10 2012-06-05 Nippon Kayaku Kabushiki Kaisha Ultraviolet-curable resin composition and use thereof

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